The present invention relates to an improved metal halide lamp of the type filling metal halide within an arc tube, and more particularly, to a high radiance ultraviolet light-source with enhanced wavelength range and intensity in the ultraviolet range used in apparatus for physics and chemistry.
One of the most widely used ultraviolet light-sources in an apparatus for physics and chemistry is the deuterium lamp. Apparatus for physics and chemistry have detection limit which depends on the radiance of the light-source. Recent demands in ultra-fine analysis require ultraviolet light-sources having high radiance. In order to meet such requirements, there has been proposed, as a high radiance ultraviolet light-source in place of the deuterium lamp, a metal halide lamp filled with tantalum halide as disclosed in Japanese Patent Laid-open No. 52-45391 laid open on Apr. 9, 1977. This lamp has a continuum spectrum in wavelengths ranging 220-450 nm, but has a low radiance in shorter wavelengths below 245 nm, and it cannot be used for the measurement in shorter wavelengths below 245 nm. For example, when a spectrophotometer is used for measuring sugar or organic acid which do not absorb the light in the near ultraviolet range, they need to be measured in wavelengths around 210 nm or shorter where the above tantalum halide lamp cannot be used.